Greek Prime Minister Alexis Tsipras hosted a meeting Wednesday with Egyptian President Abdel-Fattah el-Sissi and Cypriot President Nicos Anastasiades on the island of Crete. The talks were the sixth meeting between the three leaders aimed at forming an energy-based alliance in the east Mediterranean.

U.S. energy giant ExxonMobil will search for natural gas off the coast of Cyprus by the end of the year, a senior executive said last week.

"We have clearly expressed our support for Cyprus in its efforts to capitalize on the sovereign rights deriving from International Law regarding (offshore deposits) and to make progress in their exploitation," said Tsipras.

But Turkey has vowed to actively oppose Cyprus' campaign, insisting that the plans infringe on its own continental shelf and that they ignore the rights of Turkish Cypriots to the ethnically divided island nation's natural resources.

Cyprus was divided in 1974 when Turkey invaded after a coup by supporters of union with Greece. Only Turkey recognizes a Turkish Cypriot declaration of independence in the island's northern third.

In February, Turkey dispatched warships to block drilling by Italian energy company ENI off the Cypriot coast.

Turkey is also at odds with Egypt over boundaries in the east Mediterranean.

At Wednesday's meeting, Greek officials said the talks also covered the ongoing civil war in Syria, efforts to combat illegal immigration to Europe, and investment opportunities that include an ambitious plan to build a new Egyptian administrative capital, 40 kilometers (25 miles) east of Cairo.

The energy development plans prompted the environmental group Greenpeace to write an open letter to the three leaders, urging them to abandon fossil fuel expansion and switch to common initiatives on renewable energy.